The present invention relates to the feeding of individual document sheets to be scanned in a document scanner and, more particularly to the document delivery system which receives the scanned documents and, if desired, routes the individual sheets back to the scanning region for duplex scanning, i.e., scanning of both sides of the document sheet. As used herein, the term xe2x80x9cdocument scanning devicexe2x80x9d is intended to be broadly defined to include, but not necessarily be limited to, stand alone document copiers, facsimile machines, document scanning machines and combinations of such units.
Automatic document feed and delivery systems in large copiers capable of duplex scanning generally require a document feed path that is as long as the document that is to inverted during duplex scanning. While this is not a great disadvantage in a large piece of multi-user office equipment, in a small multi-function peripheral copier or scanning apparatus, it is of great impact on the footprint size of the apparatus. Large footprint size requires significant desk space which must be kept available. In such units, the length of the duplexing section alone approaches half of the document length. This is considerably large when duplex scanning legal size documents for example. Other disadvantages of a longer duplexing path are added cost due to additional rollers and guides to manage the extra length of media and the increased potential of document jamming due to the increased complexity. One manner of avoiding a long duplexing path is to eject the document outside the duplicating apparatus onto a tray which projects from the side of the machine. This solution also consumes space and has the added disadvantage of increased propensity for damage to the document while it is outside of the protective confines of the unit.
It is accordingly of considerable advantage to provide a more compact document scanning device by utilizing a more compact duplexing section.
The present invention provides a method of feeding and duplex scanning a document in a document scanning device comprising the steps of:
a) transporting individual sheets of said document from a stack thereof to a scan region of a scanning system;
b) scanning a first face side of said document sheet at said scan region;
c) transporting said sheet from said scan region to a pair of opposed document exit transport rollers;
d) gripping opposite face sides of said sheet in a nip between said exit transport rollers and rotating said exit transport rollers in an exit direction to pull said sheet therebetween in an exit direction to move a trailing edge of said sheet away from said scan region;
e) reversing the direction of rotation of said exit transport rollers before said trailing edge of said sheet passes therebetween to feed said sheet to said scan region in face inverted orientation for scanning a second face side of said document sheet;
f) scanning a leading portion of said second face side of said sheet and transporting a leading edge of said sheet to said nip between said exit transport rollers before a trailing edge of said sheet passes said nip in a feed direction to cause buckle formation in said sheet between said nip and said scan region;
g) again reversing the direction of rotation of said exit transport rollers to rotate said exit transport rollers in said exit direction to consume sheet buckle in said nip without causing differential slippage of adjacent leading and trailing portions of said sheet in said nip;
h) continuing to rotate a driven one of said exit transport rollers in said exit direction to pull a trailing portion of said sheet to said scan region and scanning said trailing portion of said second side of said sheet while permitting said trailing portion of said sheet to slip past a leading portion of said sheet in said nip; and
i) rotating said exit transport rollers in said exit direction to eject said sheet from between said transport rollers.
In apparatus terms, a first embodiment of the present invention comprises a duplex document scanning device comprising:
a) a document input support for holding a stack of document sheets to be scanned;
b) a document feed system for transporting document sheets to a document scan region;
c) a document scanning system for scanning individual document sheets during movement thereof through said scan region;
d) a document output support for holding scanned document sheets;
e) a document delivery system for transporting scanned document sheets from said scan region to said output support, said delivery system including a driven roller, a pinch roller opposed to said driven roller and defining a document transport nip therebetween, said driven roller having a document contact surface which has a greater coefficient of friction than the coefficient of friction of the surface of the document sheets to be transported; and
f) a drive arrangement for selectively rotating said driven roller in opposite directions.
A second embodiment of the invention provides a method of feeding and duplex scanning a document in a document scanning device comprising the steps of:
a) transporting individual sheets of said document from a stack thereof to a scan region of a scanning system;
b) scanning a first face side of said document sheet at said scan region;
c) transporting a leading edge of said sheet from said scan region into a gap between a pair of spaced document delivery rollers;
d) moving said document delivery rollers together to grip opposite face sides of said sheet in a nip between said document delivery rollers and rotating said document delivery rollers in a document delivery direction to pull said sheet therebetween and to move a trailing edge of said sheet away from said scan region;
e) rotating said document delivery rollers in a feed direction before said trailing edge of said sheet passes therebetween to feed and guide said sheet to said scan region in face inverted orientation for scanning a second face side of said sheet;
f) scanning said second face side of said sheet and transporting a leading edge of said sheet in a delivery direction toward said document delivery rollers before a trailing edge of said sheet passes said nip while moving in a feed direction;
g) separating said document delivery rollers from each other to form a gap therebetween to permit said leading edge of said sheet to pass said trailing edge of said sheet during sheet movement between said document delivery rollers;
h) allowing said trailing edge of said sheet to pass between said separated document delivery rollers and then moving said rollers together to rotate said document delivery rollers in said document delivery direction to eject said sheet from between said document delivery rollers.
The apparatus aspects of the second embodiment of the invention provides a duplex document scanning device comprising:
a) a document input support for holding a stack of document sheets to be scanned;
b) a document feed system for transporting document sheets to a document scan region;
c) a document scanning system for scanning individual document sheets during movement thereof through said scan region;
d) a document output support for holding scanned document sheets;
e) a document delivery system for transporting scanned document sheets from said scan region to said output support, said delivery system including a driven roller, a pinch roller opposed to and mounted for movement toward and away from said driven roller and defining a document transport nip therebetween;
f) a drive arrangement for selectively rotating said driven roller in opposite directions and for moving said pinch roller toward and away from said driven roller; and
g) a gate for guiding movement of said sheet between said scan region and said document delivery system.
In a third embodiment the present invention provides a method of feeding and duplex scanning a document in a document scanning device comprising the steps of:
a) transporting individual sheets of said document from a stack thereof to a scan region of a scanning system;
b) scanning a first face side of said document sheet at said scan region;
c) transporting said sheet from said scan region to a first pair of opposed document delivery rollers, said pair comprising a driven roller and an opposed first pinch roller;
d) rotating said first pair of opposed document delivery rollers in a document delivery direction;
e) causing a leading edge of said document sheet to engage a rotating sheet edge guiding surface of said driven roller to move said leading edge in engagement with said surface toward and to be gripped in a nip between said first pair of document delivery rollers to pull said sheet therebetween in a document delivery direction to move a trailing edge of said sheet away from said scan region;
f) reversing the direction of rotation of said first pair of document delivery rollers to rotate said document delivery rollers in a document feed direction before said trailing edge of said sheet passes therebetween to feed said sheet to said scan region in face inverted orientation for scanning a second face side of said document sheet;
g) scanning said second face side of said sheet;
h) transporting a leading edge of said scanned sheet in said delivery direction to engage said sheet edge guiding surface of said driven roller to cause said leading edge to move toward and be gripped in a nip between a second pair of document transport rollers comprising said driven roller and an opposed second pinch roller; and
i) continuing rotation of said second pair of document delivery rollers in said exit direction to eject said sheet from between said second pair of document delivery rollers.
The apparatus aspects of the third embodiment provide a duplex document scanning device comprising:
a) a document input support for holding a stack of document sheets to be scanned;
b) a document feed system for transporting document sheets from said document input support to a document scan region;
c) a document scanning system for scanning individual document sheets during movement thereof through said scan region;
d) a document output support for holding scanned document sheets;
e) a document delivery system for transporting scanned document sheets from said scan region to said output support, said delivery system including a driven roller having a surface for engaging and moving the leading edge of a document sheet in the direction of rotation of said driven roller, a first pinch roller opposed to said driven roller and defining a first document transport nip therebetween and a second pinch roller opposed to said driven roller and defining a second document transport nip therebetween; and
f) a drive arrangement for selectively rotating said driven roller in opposite directions.
FIGS. 1a through 1j are sequential schematic side elevation cross sectional views of a document feeder according to the present invention showing progress of a duplex scanned document therethrough in accordance with a first embodiment using document buckling and differential slippage through opposed exit drive and pinch rollers.
FIGS. 2a through 2f are sequential partial schematic side elevation views of a second embodiment using a moveable pinch roller and a document guide gate.
FIGS. 3a through 3c are sequential partial schematic side elevation views of a third embodiment using a three roller document transport with crenellated center roller.